This invention relates to a pinion shifting arrangement and, more particularly, to a shift mechanism for sliding a pinion for transmitting a drive force to an engine ring gear in an engine starter for starting an automotive engine, for example.
Heretofore, a starter motor for starting an automotive internal combustion engine as illustrated in FIG. 1 has already been well-known.
The conventional starter motor 1 shown in FIG. 1 comprises a d.c. motor 2, a pinion movement unit 3 slidably mounted on an extension (called output rotary shaft hereinafter 2a of the armature rotary shaft extending in an axially front (the right side as viewed in FIG. 1) direction from the armature of the d.c. motor 2, a solenoid switch unit 4 mounted on a side portion of the d.c. motor 2, and a shift lever 5 for slidably shifting the pinion movement unit 3.
The solenoid switch unit 4 comprises a cylindrical case 6 having a wall 6a at one end, and a cylindrical bobbin 8 on which an excitation coil 7 wound around the outer circumference thereof is disposed. A sleeve 9 is inserted into the inside of the bobbin 8, and the front end of the sleeve 9 is fitted and extends through a central opening of the wall 6a of the case 6 and is forwardly open. Within the front end side of the sleeve 9, a movable plunger 10 is disposed, and a stationary core 11 is disposed in opposition to the plunger 10 at the rear end side of the sleeve 9. A return spring 12 is disposed between the plunger 10 and the stationary core 11, so that the plunger 10 is returned to its original position when the excitation coil 7 is deenergized.
The central portion of the stationary core 11 has formed therein a through hole, into which a rod 13 is slidably inserted with its one end projecting therefrom by a predetermined distance toward the plunger 10, and with its the other end having supported thereon a movable contact 14. Also, in the plunger 10 which can be attracted and moved toward the stationary core 11, a recessed portion 10a which is axially outwardly open is formed, and a piston-shaped hook 15 having formed on its rear end a flange portion 15a is slidably inserted. This hook 15 outwardly projects through the central hole of a holder 16 which closes the open end of the recessed portion 10a, and the projecting end thereof has engaged thereto an upper end 5a of the shift lever 5. A compression spring 17 which comprises a cylindrical coil spring is disposed between the holder 16 and the flange portion 15a of the hook 15 within the recessed portion 10a of the plunger 10.
Further, reference numeral 18 indicates a cap made of a resin, and 19 indicates a terminal bolt mounted to the cap 18 and having a stationary contact 19a engageable with the movable contact 14 at its inner end.
On the other hand, the pinion movement unit 3 comprises an over-running clutch assembly 20 and a pinion 21 formed integrally with a clutch inner member of the over-running clutch assembly 20. A tubular portion 22 is integrally formed on the rear portion of the clutch outer member, and the inner circumferential surface of the tubular portion 22 has formed therein splines for engaging with helical splines formed in the outer circumference of the output rotary shaft 2a. The tubular portion 22 also has on its outer circumference a lever engagement mechanism 23 with which a forked lower end portion 5b of the shift lever 5 is engaged. The lever engagement mechanism 23 comprises a cylindrical stationary engagement ring 24 and a cylindrical movable engagement ring 25, the stationary engagement ring 24 having a radially inwardly projecting front end flange portion 24a and a radially outwardly projecting rear end flange portion 24b. The front end flange portion 24a of the stationary engagement ring 24 is placed over the tubular portion 22 and is secured onto the rear wall of the clutch outer member by a stop ring. Also, the movable engagement ring 25 is slidably fitted over the outer circumference port on of the stationary engagement ring 24, and has a radially outwardly extending flange portion 25a only on the front end. Between the flange portion 25a and the rear wall of the clutch outer member, a conical spring washer 26 is disposed. The forked lower end portion 5b of the shift lever 5 is disposed within the circumferential groove defined between the flange portions 24b and 25a of the engagement rings of the lever engagement mechanism 23 to mount or ride on the mechanism 23, thereby to engage at its front and rear end faces with the flange portions 24b and 25a.
Next, the operation of the conventional starter apparatus as above described will now be briefly described.
When the key switch of the vehicle is turned on, the excitation coil 7 of the solenoid switch unit 4 is energized to generate a magnetic force which attracts the plunger 10 toward the core 11. As the plunger 10 moves the shift lever 5 is rotated and causes the pinion movement unit 3 to slide over the output rotary shaft 2a. At this time, when the pinion 21 abuts against the side surface of an engine ring gear, the rotation of the shift lever 5 is stopped but the plunger 10 is kept moving by the magnetic attraction to compress the compression spring 17. This charged spring energy of the compression spring 17 is a force which urges the pinion against the engine ring gear through the shift lever 5.
Then, due to the movement of the rod 13 pushed into the stationary core 11 upon the abuttment of the plunger 10 against the stationary core 11, the movable contact 14 engages the stationary contact 19a, whereby the power source is connected to the d.c. motor 2. As a result, the output rotary shaft 2a rotates and its rotational force is transmitted to the pinion 21 through the over-running clutch unit 20. Thus, the pinion 21 engages the engine ring gear as soon as it starts to be rotated and is moved by the spring force of the compression spring 17 over the entire stroke (a sliding movement to the engagement position in which the front end of the pinion 21 abuts against a stopper 27 to come to a stop), and the compression spring 17 causes the movable engagement ring 25 to shift at the time the hook 15 abuts against the bottom wall of the recessed portion 10a of the plunger 10, thereby applying an urging force to the conical spring washer 26 through the shift lever 5 to flex it. The conical spring washer 26 thus flexed functions to urge the pinion movement unit 3 against the stopper 27 while the starter apparatus 1 is being operated.
However, in the conventional starter apparatus, the wear of the lower end portion 5b of the shift lever 5, the wear of a stopper 27 or a stopper ring 28, or the wear of the groove in which the stopper ring 28 is inserted cause the conical spring washer 26 to be inactive (non-flexible), making it impossible to urge the pinion movement unit 3 against the stopper 27.
The fact that the pinion movement unit 3 cannot be urged against the stopper 27 means that the pinion movement unit 3 can axially freely move during the operation between the lower end portion 5b of the shift lever 5 and the stopper 27, therefore when the pinion 21 transmits the rotational force to the ring gear, the pinion movement unit 3 is moved toward the stopper 27 due to the function of the helical spline, and when the rotational force is transmitted reversely from the engine to the pinion 21 due to change in engine rotation, the pinion movement unit 3 is moved toward the shift lever lower end 5b. Therefore, during the operation of the starter apparatus, the pinion movement unit 3 is fiercely moved back and forth, generating noise and exerting large impacts to various components, and the contact between the gear teeth of the ring gear and the pinion is intermittent and not continuous, resulting in damages in the pinion or the ring gear or other parts at an early stage.